^^^^ Definitely! First go on www.disneyworld.com do a search for your dates, resort, and room type. See what comes up. If the price is lower than what you have on your reservation, get on the phone and talk to a reservations agent. They will apply the lower rate to your reservation.
OP You don't mention if your original package already has a discount applied. If so, you will not be able to add another code to that one (cannot "stack" discounts), so you'll have to find out which one is the best $$$ wise.